The invention relates to a high-voltage switching device having at least two series-connected vacuum interrupters and to a method for operating the high-voltage circuit breaker. The invention may be used, for example, in gas-insulating switching assemblies. In this context, the term xe2x80x9chigh voltagexe2x80x9d is defined as a voltage range above 1000 V.
In high-voltage switchgear, vacuum interrupters are disposed in series in specific cases on the basis of two fundamental principles, to be precise in an uncontrolled configuration according to the reference by H. Fink, and E. Sonnenschein, titled xe2x80x9cSF6-isolierte 52-kV-Mittelspannungs-Schaltanlage mit Vakuumschalterxe2x80x9d [SF6-Insulated 52-kV Medium-Voltage Switchgear Assembly Having A Vacuum Switch], etz, Vol. 115 (1994), Issue 11, pages 622-626, using control capacitors. In the uncontrolled configuration, the primary factor is the use of the vacuum switching principle at voltage levels above 36 kV, provided by disposing two vacuum switching chambers (standard chambers), which are limited to the rated voltage of 36 kV, in series. In this case, an unavoidable scatter resulting from stray capacitances in terms of the potential splitting is accepted, for financial reasons. The series configuration must therefore be configured on the basis of the vacuum switching chamber which is most severely stressed due to the inhomogeneous voltage distribution, while the other vacuum switching chamber is subjected to less voltage stress, and is thus not optimally utilized.
One example of a series configuration of two vacuum switching chambers configured with control capacitors is provided for use for railway power supplies, at a frequency of 16 2/3 Hz. In comparison with the arcing times of 10 ms/8.3 ms that occur with 50 Hz/60 Hz, the contact gaps at 16 2/3 Hz are subject to arcing times of 30 ms. The associated comparatively severe thermal stress, and the resultant severely increased erosion (burn-off) lead to a major reduction in the withstand voltage during disconnection. This effect is counteracted by connecting two vacuum switching chambers in series, and additionally controlling them capacitively, for rated voltages of, for example, 17.5 kV.
The previous configuration of series arrangements of two or more vacuum switching chambers is in principle predicated on the use of identical switching chambers, which are each switched on and off simultaneously.
The integration of the series configuration of two vacuum switching chambers as the core of a high-voltage switching device requires capacitive control, especially for use within a gas-insulated switchgear assembly. The background to this measure is linearization of the voltage distribution across the two vacuum switching chambers, although the control capacitances must not be able to have a disadvantageous influence on the extinguishing capacity, as is dealt with in the reference by T. Betz. D. Koenig, titled xe2x80x9cInfluence Of Grading Capacitors On The Breaking Capability Of Two Vacuum Circuit-Breakers In Seriesxe2x80x9d, IEEE 18th Int. Symp. on Discharges and Electrical Insulation in Vacuum, pp. 679-683, Eindhoven, The Netherlands, Aug. 17-21, 1998.
It is accordingly an object of the invention to provide a high-voltage switching device having at least two series-connected vacuum interrupters, and a method for operation of the high-voltage switching device which overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, which can be optimally utilized with regard to voltage loading. In this case, the described measures are intended to ensure that the series configuration can compensate for the influences on the disconnection capability (which differ depending on the geometry, operational conditions and environmental conditions) without having to use rigid control from the outside with the aid of control capacitors.
With the foregoing and other objects in view there is provided, in accordance with the invention, a high-voltage switching device, containing at least two series-connected vacuum switching chambers, including at least one first-type vacuum switching chamber and at least one second-type vacuum switching chamber, the first-type vacuum switching chamber and the second-type vacuum switching chamber each having a physical size and a contact configuration containing contacts with contact diameters, a separation between the contacts, and contact types, in which at least one of the physical size and the contact configuration of the first-type vacuum switching chamber being differently configured than that of the second-type of vacuum switching chamber, and the vacuum switching chambers selected such that re-ignitions and restrikes of the first-type vacuum switching chamber being coped with by the second-type vacuum switching chamber.
The advantages that can be achieved by the invention are, in particular, that the voltage distribution is achieved on the basis of a natural voltage distribution, influenced exclusively by the intrinsic and stray capacitances, and without any additional control capacitances. This avoids the compensation currents which are produced on re-ignition or restriking of a vacuum switching chamber and flow via the control capacitances, whose amplitudes rise as the control capacitance becomes larger, thus leading to heating of the contacts of the vacuum switching chambers and, in the end, reducing the disconnection capacity.
As a particular advantage, it is possible to achieve the object of coping with switching situations (short-circuit disconnection capacity, connection capacity) independently of the object of coping with the dielectric requirements, by suitable selection of the vacuum switching chambers.
The arcing behavior can be influenced directly by additional measures on the drive unit, thus allowing the introduction of a separate degree of freedom for the configuration of both the dielectric behavior and the disconnection behavior when subject to arcing influences.
The proposed measures lead to a different arcing behavior due to the combination of different vacuum switching chambers with a different physical size (different rated voltage, different disconnection current) and/or different contact configuration (different contact diameters, different separation between the contacts, different contact types), and generally different intrinsic capacitances. By deliberate use of this effect, the configuration versatility to cope with individual switching situations can be considerably increased in comparison with known configurations. If, for example, two suitable different vacuum switching chambers with different contact diameters are used in series, then the different intrinsic capacitances of the vacuum switching chambers and the different arcing behavior can advantageously be combined with the aim of increasing the switching capacity.
The background to the use of series connected vacuum switching chambers is the desire to exploit both the technical advantages of the vacuum circuit-breaker in the form of a high di/dt and du/dt disconnection capacity (di/dt=current grading, du/dt=voltage grading) and the economic advantages, such as freedom from maintenance, low drive energy and compact construction. These advantages are particularly pronounced in the case of vacuum switching chambers with short contact separations between the contacts and, by linking two or more vacuum switching chambers, and thus switching paths, in series, can be used to allow vacuum switching chambers to be operated even at higher rated voltages, beyond the 36 kV voltage range. This results in possible alternatives to sulfur hexafluoride (SF6) which, until now, has been the dominant extinguishing medium in the voltage range above 36 kV, and these alternatives are also of interest in terms of environmental aspects.
The high-voltage switching device may also contain a housing; a series connection of at least two vacuum interrupters (i.e. quenching chamber or combination of quenching and switching chamber); disposed in the housing; and insulation disposed in the housing between the chambers and the housing, the insulation being selected from the group consisting of SF6, N2, air, gaseous dielectrics and liquid dielectrics.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a high-voltage switching device having at least two series-connected vacuum interrupters, and a method for operation of the high-voltage switching device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.